Hearth-type furnace, particularly siemens-martin furnace



Sept. 7, 1965 F. BARTU 3,204,938

HEARTH-TYPE FURNACE, PARTICULARLY SIEMENS"MARTIN FURNACE Filed July 11,1965 2 Sheets-Sheet 1 x INVENTOR 'F'Rmz Bh w BY Sept. 7, 1965 F. BARTU3,204,938

HEARTH-TYPE FURNACE, PARTICULARLY SIEMENS-MARTIN FURNACE Filed July 11,1963 3 Sheets-Sheet 2 I 77 I l 75 4 O 78 15 O 15 3 i 2 I I Q I 12 \1 LINVENTOR Fn inwz BH BY 7522M w. ii--- United States Patent 3,294,938HEARTH-TYPE FURNACE, PARTICULARLY SIEMENS-MARTIN FURNACE Franz Bartu,Kusnacht, Switzerland, assignor to Maerz Ofenbau AG., Zurich,Switzerland, a corporation of Switzerland Filed July 11, 1963, Ser. No.294,308 Claims priority, application Austria, July 16, 1962, A 5,721/628 Claims. (Cl. 263-46) The present invention relates to an improvedhearthtype furnace, particularly a Siemens-Martin furnace.

In a Siemens-Martin furnace the fuel and the combustion air cometogether at the burner head. It is advantageous from the standpoint offlow technique considerations to introduce the combustion air as near aspossible to the fuel jet. Additionally, it is also desirable for thecombustion and flame direction or regulation to impart to the aircurrent a specific impulse for which it is necessary to have a suitableair velocity and a correspondingly smaller outlet cross-section for theair. For these reasons the inside width of the burner head is alwayssmaller than the inside width of the adjoining heating chamber.

The transition from the back wall and the front wall to the side wallsof the burner head form the so-called hearth pillars, which are verticalor nearly vertical walls which enclose an acute angle with thelongitudinal axis of the furnace and constrict the cross-section of theheating chamber towards the burner head. With specific burner headconstructions the hearth roof or dome must also be pulled or directeddown towards the burner head and the annexing burner head dome must bearranged at an inclination to the hearth. The slopingly arranged hearthpillars and the inclined domes at the transition from the burner head tothe hearth are advantageous for the flow process of the combustion airand the flames. However, they form at the escape or draw-01f side of thefurnace a constrictive region for the stream of smoke gas and, thus, aresubjected to pronounced wear. 'The slopingly arranged hearth pillars andthe inclined dome sections have still a further disadvantage whichalways becomes more readily descernable: The brickwork of thesuperstructure of the furnace must always be renewed in periods ofseveral months to a year. The influence of the furnace preparation orlining costs on the production costs for steel is always becominggreater with the continuous increase of Wages. For this reason, in thefurnace construction art, it is attempted to get along with as few andsimple brick forms as possible, to reduce the storage of refractorymaterial, to limit the trim Work during the furnace preparation orlining operation, and for such reasons to make the furnace shape assimple as possible.

It has already been proposed in the art to impart to the superstructureof the furnace at box-type shape, to build the burner heads with thesame inner width as the heating chamber and to construct the side wallsof the burner head in the form of linear extensions of the forward andback or rear walls while dispensing with the hearth pillars.Additionally, the disposing of the inclination of individual domesections is always more and more desired. In the previously undertakenproposed simplifications one knowingly accepted flow techniquedisadvantages which unfavorably influenced the'course of combustion andthe direction of the flame path. In particular, it was not possible tofind a satisfactory solution for the arrangement and construction of theshafts.

In accordance with the proposals known at the present time, the width ofthe burner head is brought to the width of the heating chamber and theforward and rear end shaft walls are moved away from one another to thesame extent so that these shaft walls and the side walls of the burnerhead remain in a plane. As a result, there is engendered a series ofdisadvantages. The separation of both shafts with double shaft furnaces,or the enlargement of the shaft with a single shaft furnace, to theWidth of the heating chamber, of necessity, requires a longer slagpocket or chamber than usual. The elongation of the slag pocketincreases construction costs of the furnace and, in many, if not in themajority of steel mills, is not at all possible to carry out becausewith the elongation of the slag chamber the checker chamber must also befurther displaced towards the reversal equipment and the available spacein the steel mills, only in the most rare instances, permits such adisplacement.

In a single shaft furnace such an expansion or enlargement of the shaftresults in unequal air impingement at the cross-section of the shaft,because the air from the slag chamber of the shaft is not directed inthe direction of the lengthwise axis of the hearth, but rather, isdirected at a right angle thereto. The front wall side portion of theshaft receives less air than the rear wall side and this irregularity iscontinued to the heating chamber, in which the flame at the one sideburns with excess air and at the other side with a deficiency of air.The irregular air distribution can also lead to a deflection of theflame toward the rear wall and to greater wear of this furnace portion.The greater the width of the air shaft, then the greater the distancethat the combustion air must be sucked up by the oil burner, then alsothe greater the tendency for the burner to work as injector upon thesmoke gases located in the heating chamber. The trail of the smoke gasesbecomes larger, the flame temperatures lowered and the service life ofthe lining lowered, because due to the trail of the smoke gases alwaysnew FeO-particles are guided to the refractory lining. A furtherdisadvantage of such a wide shaft resides in the large dimensions of theshaft reflecting walls, the durability of which decreases and the brickconsumption of which increases.

A portion of the enumerated disadvantages also occurs with the previousproposed widening of the burner head of a double shaft furnace. In thiscase there is also present as a further disadvantage the widening of theflame bridge between the air shafts, the wider it is that much more dustand slag deposit, and with increasing width becomes very diflicult tomaintain clean.

Accordingly, the present invention has as one of its primary objects toeffectively prevent or minimize such disadvantages.

A further important object of the present invention is to provide animproved construction of a hearth-type furnace, in particular aSiemens-Martin furnace, which is economical to construct and repair,permits the use of a small number of brick shapes for the furnacesuperstructure so that the storage of such bricks and the supportingstructure therefor is considerably simplified.

Another important object of the present invention is to provide animproved construction of a hearth-type furnace permitting the latter toassume a substantially boxshaped configuration, thereby facilitatingrelining of the furnace and generally improving the economics ofproduction and maintenance of such furnace.

A further important object of the present invention is the provision ofa Siemens-Martin furnace or the like, wherein the cross-section of thefurnace superstructure with the exception of the base is substantiallyuniform from one end wall to the other.

Still another important object of the present invention is the provisionof a Siemens-Martin furnace or the like, wherein the inner width betweenthe forward and back walls or outermost walls of the shaft means closestto the respective forward and back walls of the furnace superstructureis smaller than the inner width of the burner head of the aforesaidfurnace superstructure as measured at the plane of the mouth or openingof said shaft means.

The furnace of the present invention is characterized by the featuresthat the cross-section of the superstructure of the furnace with theexception of the hearth base, remains continuously the same from endwall to end wall, that the front wall and rear wall are inwardlyinclined and the inner spacing between the forward wall. side and therear wall side of the shaft means is smaller than the inner width of theburner head profile, measured at the plane of the mouth of the shaftmeans.

Theblind angle or space between the opening or mouth of the shaft andthe receding burner head walls can, for example, be filled with agranular refractory material.

The burner head thereby has imparted to it, apart from the hearth base,the same profile as the heating chamber, whereby the side walls of theburner head at their crown or top possess approximately the same spacingas the forward and rear side walls of the shafts. In other Words, thespacing of the forward and rear side walls of the shafts substantiallycorresponds to the width of the furnace dome.

The form, size and position of the shafts, the opposite situated domeand the upper portion of the side walls of the burner head aredeterminative for the guiding of the combustion air. Since the positionand form of the shafts remains unchanged and by virtue of the inwardinclination of the side walls of the burner head their spacing at thetop in comparison with the classical constructional forms also does notexperience any marked change, the flow process in the working or outletside of the burner head is not disadvantageously influenced in spite ofthe separation of the burner head walls at the base.

Still further objects and the entire scope of applicability of thepresent invention will become apparent from the detailed descriptiongiven hereinafter; it should be understood, however, that the detaileddescription and specific examples, while indicating preferredembodiments of the invention, are given by way of illustration only,since various changes and modifications within the spirit and scope ofthe invention will become apparent to those skilled in the art from thisdetailed description.

In the drawings wherein like reference numerals generally denote similarelements:

FIGURE 1 illustrates a fragmentary, cross-sectional view taken alonglines II of the furnace of FIGURE 2;

FIGURE 2 is a fragmentary, cross-sectional view taken along the linesIIII of FIGURE 1;

FIGURE 3 is a cross-sectional view taken along lines IIIIII of FIGURE 2;

FIGURE 4 is a cross-sectional view taken along lines IV IV of FIGURE 2;

FIGURE 5 is a fragmentary view showing details of a modified form offurnace port end, particularly a furnace with an inclined burner headand inclined shaft means;

FIGURE 6 is a fragmentary view showing details of a further design offurnace port end, wherein the shaft is vertical and the end walls of thefurnace are inclined; and

FIGURE 7 is a cross-sectional view substantially similar to FIGURE 4,illustrating details of the brickwork and support structure.

In the drawings there is generally illustrated the furnacesuperstructure of a reverberatory hearth-type furnace, particularly aSiemens-Martin furnace, provided by way of illustration and notlimitation, with a doubleshaft or uptake, and depicting the relativelysimple furnace shape achieved by following the teachings and underlyingprinciples of the present invention. For purposes of simplifying theexplanation and illustration of the invention, only enough of thefurnace structure has been shown to enable one skilled in the art toreadily appreciate the inventive concepts and to fully understand thedescription to follow.

Describing now FIGURES 1 to 4, reference numeral 1 generally denotes thehearth brickwork of the superstructure of the furnace F to which isconnected side walls in the form of a forward wall 2 and a rear or backwall 3, both of which are inwardly inclined, as best seen in FIGURES 2and 3. Between both of the side walls 2 and 3 there extends the roof ordome 4. Directly adjacent to and flush with one end wall 5 there extendsinto the furnace or heating chamber 7 a pair of air shafts or upstakes6. The shafts 6 open into the burner head region, generally designatedby numeral 10, at a plane AA taken through the respective opening ormouth of said shafts. The region of the furnace superstructure lyingbeneath the plane AA can be conveniently considered as the base portionof the aforesaid superstructure.

Both of the side walls 2 and 3 advantageously extend from one end wall 5to the other end wall (not shown) with the same inclination and the samecurvature. For convenience in illustration there is only shown one endof the furnace superstructure, but it is to be appreciated, and as willbe apparent to those skilled in the art, a substantially similararrangement of shafts and burner head are provided at the opposed portend of the furnace. The height of the walls 2 and 3 is advantageouslythe same throughout the entire length of the furnace, as can be readilyascertained by comparing FIGURES 3 and 4. Thus, for the construction ofthe forward and rear walls 2 and 3, respectively, only a single brickshape or format is necessary. This is also true for the dome 4, likewiseconstructed from end wall to end wall of the furnace with the samecurvature and the same Width. The parting surfaces between the brickassembly of the walls 2, 3 and that of the dome 4 lie at the sameheight, that is, all individual parting surfaces between thecorresponding walls 2, 3 and dome 4 form a plane, as generally indicatedin FIGURES 3 and 4 by the lines B-B and C--C.

In the embodiment illustrated in FIGURES 1 to 4, the walls of the shaftmeans 6 here depicted for example as a double-shaft arrangement, areinclined as shown, to provide the proper direction of air inflow, aswill be further explained shortly hereinafter. The outermost walls 6aand 6b of the shafts 6, that is, the respective walls of the shaftsclosest to and extending in substantially the direction of the front andrear walls 2 and 3, respectively, are spaced from one another at aninner distance or width X which is less than the inner width Y of theprofile of the burner head 10 (see FIGURE 3), as measured in the planeAA of the mouths of the shafts 6 as well as substantially correspondingto the width of the dome 4. In other words, the outermost walls of theshaft means 6 are spaced from one another to provide an inner width orspacing X which is less than the inner width or spacing Y of the frontand rear walls of the burner head 10 of the furnace superstructure, asmeasured along the plane AA of the mouth of the shaft means 6, that is,the location where the latter open into the burner head 10. In the eventof a single shaft arrangement this aforementioned relationship wouldalso be maintained. The dead spaces or blind angle 13 between theoutermost walls 6a, 6b of the shafts 6 and the associated side walls 2,3 can advantageously be filled, if desired, with a granular refractorymaterial, as indicated, at 14, in FIGURE 3.

The angle between the air currents out of the shafts 6 and the dome 4above said shafts is of importance for the flow process of thecombustion air. This angle should not exceed a specific value. In orderto maintain such angle with the desired limits, the shafts 6 areadvantageously positioned to be inclined with a dome having horizontalzenithal or top lines, for example as shown in the arrangement ofFIGURE 1. The end wall 5 of the furnace can remain vertical, in themanner shown. However, it is also possible that such end wall receivethe same inclination as the shafts. Such an arrangement is shown, by wayof example, in FIGURE 5 wherein the walls 60 of the double shaft means6d are inclined and merge with a furnace end will 5a which is similarilyinclined. It is, however, also possible to leave the shaft meansperpendicular and only to inwardly incline the end wall, since then alsothe angle of impact between the air currents which emanate from theshaft means and the dome is smaller than 90". Such an arrangement isshown, by way of example, in FIGURE 6 wherein the double shaft means 62is provided with vertical shaft walls 6 merging with an inwardlyinclined end wall 5b of the furnace.

In FIGURE 7 there are depicted details of the support arrangement forthe front and rear walls 2 and 3, respectively, as well as the dome 4 ofthe furnace superstructure. Advantageously, the walls 2, 3 and dome 4are formed of suitable brickwork 15 arranged in individual sections orgroups 20. These brickwork sections 20 are arranged alongside oneanother and extend the length of the furnace (see FIGURES l and 2). Thebrickwork of each section of the walls 2, 3 and 4 are advantageouslysupported by individual segments or elements 16, 17 and 18,respectively, with the support elements of any one wall being similar toone another and interchangeable. The support elements 16, 17 and 18 ofeach brickwork section are suspended on I-beam 19 or the like extendinglengthwise of the furnace. For further details of such a possiblesupport arrangement for the furnace brickwork, attention is directed tothe commonly assigned, United States Patent No. 3,088,722, granted May7, 1963, to Alfred Slesaczek for Wall Construction and Mounting Thereoffor Industrial Furnaces. Particular advantages result with thereinforcement or armament of the furnace, especially then, when thewalls 2, 3 and the dome 4 are assembled from prefabricated brickworkstrips. The indivdual steel segments 17 of the dome 4 at which thebricks 15 are suspended are advantageously similar to one another, asare the support segments 16 and 18 for the side walls 2 and 3respectively. Such an arrangement has the result of providing aconsiderable simplification of the furnace construction, of the storageof materials, and a mutual interchangeability of the individual segmentsof each wall section.

While there is shown and described present preferred embodiments of theinvention, it is to be distinctly understood that the invention is notlimited thereto but may be otherwise variously embodied and practisedwithin the scope of the following claims.

Having thus described the present invention, what is desired to besecured by United States Letters Patent, is:

1. Hearth-type furnace including a furnace superstructure provided witha front wall, a rear wall, a dome and opposed end walls, said front andrear wall being inwardly inclined, said walls defining a space ofsubstantially constant cross section from one end Wall to the other endwall, shaft means of relatively small cross-section communicating withsaid space beneath said dome,

said shaft means having outermost walls extending substantially in thedirection of said front and rear wall, with the spacing between saidoutermost walls being less than the spacing between said front and rearwall of said furnace superstructure and substantially corresponding tothe width of the dome.

2. Simens-Martin furnace including a furnace superstructure comprising afront wall, a rear wall, a dome and opposed end walls, said front andrear wall being inwardly inclined, said furnace superstructure having anupper portion and a base portion, said upper portion being ofsubstantially constant cross-section from one end wall to the other andwall, double shaft means opening from below into said upper portionbeneath said dome, said double-shaft means including outermost wallsextending substantially in the direction of said front and rear wall,the spacing between said outmost walls being less than the inner spacingbetween said front and rear wall of said furnace superstructure andsubstantially corresponding to the width of the dome.

3. Siemens-Martin furnace including a furnace superstructure having afront wall, a rear wall, a dome and opposed end walls, said furnacesuperstructure including at least one burner head and a heating chamber,double shaft means including mouth means opening into said burner headbeneath said dome, said mouth means being flush with the associated endwall, the portion of the furnace superstructure disposed beneath a planecontaining said mouth means of said shaft means defining the base ofsaid furnace superstructure, the cross-section of said furnacesuperstructure above said plane and extending from one said end wall tothe other being substantially constant throughout, said double-shaftmeans being defined by outer walls extending in the direction of saidfront and rear wall which are spaced from one another a distance lessthan the inner width of said burner head between said front and rearwall measured along said plane of said mouth means and approximatelycorresponding to the width of said dome.

4. Siemens-Martin furnace including a furnace superstructure providedwith a front wall, a rear wall, a dome and opposed end walls, said frontand rear wall being inwardly inclined and formed of bricks arranged insections alongside one another, prefabricated support elements forcarrying said bricks of each section, said prefabricated supportelements of any one front and rear wall being similar to one another andinterchangeable, said furnace superstructure comprising at least oneburner head, a heating chamber and a base portion, the portion of saidfurnace superstructure disposed above said base possessing asubstantially uniform cross section from one end wall to the other endwall, double-shaft means including mouth means opening from below intoburner head beneath said dome, said double-shaft means being ofrelatively small cross-section to provide relatively high flowvelocities for air and are bounded by outer walls extending in thedirection of said front and rear Wall, said outer walls being spacedform one another a distance substantially equal to the width of the domeas well as a distance less than the inner width of said burner headbetween said front and rear wall measured along a plane containing saidmouth means.

5. Siemens-Martin furnace according to claim 4 wherein said double-shaftmeans are inclined in the direction of said heating chamber.

6. Siemens-Martin furnace according to claim 4 wherein said double-shaftmeans are vertical and the end wall of the associated burner head isinclined in the direction of said heating chamber.

7. Siemens-Martin furnace according to claim 4 wherein said double-shaftmeans and the end wall of the associated burner head are inclined in thedirection of said heating chamber.

8. Siemens-Martin furnace according to claim 4 wherein said dome isformed of bricks arranged in sections along- References Cited by theExaminer UNITED STATES PATENTS 1,513,828 11/24 Kernohan et al. 263-151,735,606 11/29 Fitch 263-15 1,752,374 4/30 Durrer et a1. 263-15 8Danforth 263-15 Stevens 26315 Egler 26315 Brashear 263-15 Luellen 263-15Bartu et a1. 263 46 Heuer 26346 Slesaczek 263-46 WILLIAM F. ODEA, ActingPrimary Examiner.

CHARLES SUKALO, JOHN J. CAMBY, Examiners.

1. HEARTH-TYPE FURNACE INCLUDING A FURNACE SUPERSTRUCTURE PROVIDED WITHA FRONT WALL, A REAR WALL, A DOME AND OPPOSED END WALLS, SAID FRONT ANDREAR WALL BEING INWARDLY INCLINED, SAID WALLS DEFINING A SPACE OFSUBSTANTIALLY CONSTANT CROSS SECTION FROM ONE END WALL TO THE OTHER ENDWALL, SHAFT MEANS OF RELATIVELY SMALL CROSS-SECTION COMMUNICATING WITHSAID SPACE BENEATH SAID DOME, SAID SHAFT MEANS HAVING OUTERMOST WALLSEXTENDING SUBSTANTIALLY IN THE DIRECTION OF SAID FRONT AND REAR WALL,WITH THE SPACING BETWEEN SAID OUTERMOST WALLS BEING LESS THAN THESPACING BETWEEN SAID FRONT AND REAR WALL OF SAID FURNACE SUPERSTRUCTUREAND SUBSTANTIALLY CORRESPONDING TO THE WIDTH OF THE DOME.